The present invention relates to a process for the preparation of hydroxylated lecithin from crude soybean lecithin.
The invention particularly relates to a simple and rapid microwave-assisted process for the preparation of hydroxylated lecithin from soybean lecithin. The commercial soybean lecithin is hydroxylated very rapidly using hydrogen peroxide and lactic acid in microwave irradiation conditions compared to traditional thermal reaction conditions. Microwave heating has the unique feature of providing environmentally friendly processes.
Commercial soybean lecithin is an important co-product of oil processing obtained during degumming step of oil refining. Soybean lecithin is a complex mixture and comprises phospholipids, triglycerides, with minor amounts of other constituents like phytoglycolipids, phytosterols, tocopherols and fatty acids. The major phospholipids present in vegetable lecithins are phosphatidylcholine, phosphatidylethanolamine and phosphatidylinositol. Soybean lecithin has potential as a multifunctional additive for food, pharmaceutical and industrial applications. The primary usage of Soybean lecithin in food is as an emulsifier. (Dashiell, G. L., in Lecithins: Sources, Manufacture and Uses (AOCS Monograph), edited by B. F. Szuhaj, American Oil Chemical Society, Champaign III, 1989, p. 213). An effective way to improve water dispersability or enhance emulsifying properties of vegetable lecithins for o/w system is hydroxylation. The pronounced xe2x80x9chydrophilicxe2x80x9d character enables the products to be dispersed easily in cold water. Hydrogen peroxide reacts with the double bonds of unsaturated phospholipid fatty acids under the catalytic action of organic acids of low molecular weight (e.g., lactic acid) to form dihydroxy fatty acid derivatives. Hydroxylation imparts hydrophilic properties and improves moisture retention to the lecithin. Hydroxylated lecithin is a light colored product with increased water dispersability. It is useful in baking applications where it can improve the dispersion of fats and retard staling (Schmidt, J. C, and Orthoefer, in Lecithins, edited by B. F. Szuhaj and G. R. List, American Oil Chemical Society, Champaign III, 1985, pp. 203-211).
Hydroxylation involves insertion of hydroxyl groups at the points of unsaturation in phospholipid fatty acid [U.S. Pat. No. 2,629,662 (1953)]. This process involves blending of 14% of 100-volume hydrogen peroxide in the presence of an organic acid such as lactic acid or peracetic acid or tartaric acid or citric acid at elevated temperatures (40 to 75xc2x0 C.) for about 10% reduction in Iodine Value in about 1 to 3 hours of reaction time. The inventors used very high concentration of hydrogen peroxide for the hydroxylation reaction and the phospholipids may get degraded due to the exposure of the lecithin to higher temperatures for longer reaction periods.
The objective of the present invention is to provide an improved process for the hydroxylation of crude soybean lecithin using lower concentrations of hydrogen peroxide solution with higher conversion rates at lower reaction times. The Iodine Value reduction of the crude soybean lecithin through microwave-assisted reaction in 40 minutes is about 37%, which could not be achieved using the conventional heating even after 18 hr in similar reaction conditions. Similarly less than 5 minutes time is sufficient to achieve 10% reduction in IV of hydroxylated lecithin.
The main objective of the present invention is to provide an improved process for the hydroxylation of crude soybean lecithin.
Another objective of the present invention is to develop a simple environmentally friendly method wherein microwave irradiation technique is used instead of traditional thermal heating.
Yet another objective of the present invention is to use lower concentration of hydrogen peroxide (30%) as the high concentrations tend to cause decomposition of lecithin.
Yet another object of the present invention is to bring down the hydroxylation time drastically with enhanced hydroxylation using microwave irradiation technique without exposing the lecithin to longer hours of reaction.
Accordingly the present invention provides an improved process for the preparation of hydroxylated lecithin from soybean lecithin, which comprises hydroxylating crude soybean lecithin by using about 30% hydrogen peroxide in the range of 1-4 w % of lecithin and about 75% lactic acid in the range 12-18 w % of lecithin, as hydroxylating agent through microwave irradiation, at a temperature ranging between 50 to 70xc2x0 C., at microwave power of 300 to 600 W for a period of 5-60 min to obtain the desired product. In an embodiment of the present invention the starting material used is crude soybean lecithin. In an another embodiment the amount of hydrogen peroxide used in the reaction mixture is preferably 3% of lecithin. In yet another embodiment the amount of lactic acid peroxide used in the reaction mixture is preferably 15% of lecithin. In yet another embodiment the reaction is carried out preferably at 300 to 600 W microwave power. In yet another embodiment the reaction is carried out preferably for a period in the range of 5-40 min. In still another embodiment the reduction of iodine value in hydroxylated lecithin is about 20 to 37%.